There are different ways to configure multiple sites on one install. Often they are completely segregated, meaning you would simply install babel on those sites independently.
Are the other sites separate folders on your server? I don’t know the tech side well but my admin has like 2-3 sites that are with my ‘main’ site but independent. They have their own login and backend. Maybe you don’t have this structure, I am not sure. I guess they are multiple ‘installs’, but on the backend I have one main one and then the folders.
Are these sites sharing any templates or other resources? Maybe you can tell us a bit more about your setup.
Other more knowledgeable people will be around tomorrow. This new forum has been great for providing really good info
To check, look at the extras you are using on the main one. If you are truly doing this all one one install you’ll have something, I think, which delivers that functionality.
Let’s wait for better advice than I can give